However, the report, which was published last week, was more positive than a very similar study Which? carried out two years ago about peat-free composts in general.
This is a marked contrast to comments made in 2008 when Which? said “there is a large gulf between the performance of peat-free and peat-based composts for growing young plants from seed” (see letsrecycle.com story).
The new report praised some peat free composts – such as the New Horizon growbag – which was classified as a “best buy”, as it was in 2008, and scored higher than some composts containing peat in a test to see which composts worked best for sowing seeds.
Peat-free composts occupy the bottom half of the table for sowing seeds with scores ranging from 33% (the lowest) to 50% with New Horizon being the exception, as it was in the 2008 trials. For growing young plants, peat-free composts scored no higher than 58% with the top six composts being peat-based.
Peat-free composts are made up of materials such as green waste, composted bark and a substance called coir – fibres from coconut shells. Gardeners are increasingly being urged to use peat-free composts as it is believed harvesting peat bogs is damaging to the environment.
The New Horizon growbag, which contains around one-fifth green waste from a variety of sources, came third from top for sowing seeds in the review with a score of 71% and the report said that even “tricky” petunia seeds germinated well in this product and developed into “good quality seedlings”. The growbag came eight in a test for growing young plants with a score of 58%.
However, other peat-free products did not fare so well. Vital Earth seed and cutting compost, which contains less than 25% green waste, was classified as a “don't buy”. It came 11th out of 12 and scored 38%, 5% higher than Homebase multi purpose peat-free compost which was 12th.
The report said: “These two composts performed poorly overall in our seed trial. Petunia seeds in particular struggled to germinate. Only 35% of our seeds germinated in Homebase multi purpose peat free compost and 38% in Vital Earth seed and cutting compost.”
However, in a test to see how compost performed when growing young plants the Vital Earth product scored 54% – just 4% less than the New Horizon growbag. The Homebase compost scored 13%.
Responses
Marianne Stokes, sales and marketing manager at Vital Earth, said the company was “surprised” and “bitterly disappointed” by the report and would be investigating the issue.
She added: “It flies in the face of reports we have had from other consumers. One of our buyers in the south west has said before that our product works better than anything he has ever used. It is the first time we have had a negative trial.”
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